The spin cycle of a washing machine removes water centrifugally from wet clothes by spinning the clothes at high speed in a spin basket. In order to reduce the possibility of injury to the user during the spin cycle, it is known to use an electronically actuated lock for holding the washing machine door in the closed position.
U.S. Pat. Nos. 6,363,755; 5,823,017; and 5,520,424, assigned to the present assignee and hereby incorporated by reference, describe several locking mechanisms. Desirably, the locking mechanism minimizes projecting parts on the washing machine door which might snag clothing or reduce access to the spin basket, and is simply integrated into the washing machine housing.
A signal indicating the state of the washing machine door as opened or closed may be used to ensure the door is closed before the lock bolt is engaged. Such a signal may be provided by a switch communicating with the washing machine door. Ideally such a switch could not be easily defeated, would operate reliably when used with other washing machine components with normal manufacturing tolerances, and would be resistant to contamination by water and dirt.
U.S. Pat. No. 7,493,783, hereby incorporated by reference, describes a door lock that can sense whether the door is closed by distinguishing between an “over-travel” position of the bolt that can occur when the bolt is extended and the door is up and so does not block the extension of the bolt, and an “engagement” position of the bolt that occurs when the door is down and the bolt is received by the door blocking overextension of the bolt. An appliance controller, by distinguishing between three electrical signals indicating, respectively, the unlock position, the over-travel position, and the lock position, can determine that the door is properly locked with the bolt engaging the door.
Many existing controllers do not have the capability to accommodate additional signals and respond to those signals by retracting the lock. Alternatively, it may be desirable to avoid the extra wiring necessary to communicate an over-travel position to the appliance controller.